kevinliu18
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Measuring Bacteria

Postby kevinliu18 » Tue Dec 31, 2013 3:41 pm

Is there a way to measure bacterial or virus on a solid surface? I am doing a science project that requires this

JMP
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Re: Measuring Bacteria

Postby JMP » Wed Jan 01, 2014 9:07 am

Hi Kevin,

The most common way would probably be to swab your solid surface and then rub that swab over a petri dish with bacterial growth agar. Then you just let the plates incubate and grow.

Keep in mind that different types of bacteria grow on different growth mediums and at different temperatures, etc. One general growth medium is LB agar, but you might want to use a different one if you are looking for particular types of bacteria. Plates are usually grown at 37 degrees Celsius (this is essentially body temperature), but again, that will depend on the specific bacteria you are looking at.

Please also keep in mind that you will not to use appropriate controls and be very consistent with how you do your swabs. For example, you'll need to choose the size of the area you are going to swab and keep that equal through all of your samples.

I hope this helps, and please feel free to post again if you need more help!
Have fun with your experiment!
JMP

kevinliu18
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Re: Measuring Bacteria

Postby kevinliu18 » Sat Jan 04, 2014 8:01 pm

Thanks, I thought of that -its a good idea- I did this in class before and we definitely saw results. However is there a "machine/measurer" that can detect the amount of bacterial with little time? I remembered that I saw something on the news where they shone a light on a surface and the bacterial colonies "glowed".

Thanks,
Kevin

JMP
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Re: Measuring Bacteria

Postby JMP » Wed Jan 08, 2014 8:14 am

Hi Kevin,

I don't think what you are describing will work for you. Sometimes scientists modify bacteria, and one of those modifications can make them glow under certain light. Although I don't know exactly what you saw, I suspect it was something like that, where specific bacteria that had been modified to glow under special lights where shown on a surface, but this will not work with regular bacteria. If you want to find out the number of bacteria (of any kind) on a surface, the best method is still to swab and plate.

Sorry.

JMP

kevinliu18
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Re: Measuring Bacteria

Postby kevinliu18 » Wed Jan 08, 2014 10:59 pm

no problem. I appreciate you help :) Any tips on the bacteria project

kevinliu18
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Re: Measuring Bacteria

Postby kevinliu18 » Sun Feb 16, 2014 7:21 pm

HI, My group and I are thinking of measuring effectiveness of soaps based on ingredients. I know some of then contain tricolsan (sorry for spelling) and some contain other ingredients. Does anyone have a list of the active ingredients/brands that I can reference from? I also need some bacteria to experiment with (particularly those that tend to cause cold/harmful and hand soaps kill/eliminate) do you know where I can get those and any specific names that would be appropriate (other than E-coli)?

Thanks and your prompt response will be appreciated,
Kevin

SciB
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Re: Measuring Bacteria

Postby SciB » Mon Feb 17, 2014 12:12 pm

Hi Kevin,

If you need to count bacteria accurately you need to make serial dilutions of your bacterial cultures, plate them on nutrient agar, let them grow for a couple days then count the number of colonies. Here is a site that describes how to do that:

http://www.science-projects.com/serdil.htm

Here are a couple of videos that you might also find helpful to see how this is done in the lab:

http://www.youtube.com/watch?v=teV7rlBkpQU
http://www.youtube.com/watch?v=ZqdU3VfQ_Tc

If you need more help with this, please let us know.

Good luck!

Sybee

kevinliu18
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Re: Measuring Bacteria

Postby kevinliu18 » Tue Feb 18, 2014 12:07 am

Thanks, any recommendation on a specific type of bacteria to use an how to get them (e.g. purchase?)?

SciB
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Re: Measuring Bacteria

Postby SciB » Tue Feb 18, 2014 3:38 am

Sure. The most commonly used SAFE type of lab bacteria is the K12 strain of Escherichia coli, the human gut bacterium. You can get cultures of E coli K12 from Carolina Biologicals: http://www.carolina.com/bacteria/escher ... i+cultures

If you are going to test various soaps or other products for killing bacteria, you will also need nutrient agar plates to grow the E coli on. Carolina also sells them: http://www.carolina.com/prepared-biolog ... gar+plates

The active ingredients of an antibacterial product are given on the label. Otherwise, go to the company's website or call them.

If you haven't already done so, read the guide to working safely with bacteria: http://www.sciencebuddies.org/science-f ... fety.shtml

Also check out this project: http://www.sciencebuddies.org/science-f ... p014.shtml

If you have more questions, please let us know.

Sybee

kevinliu18
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Re: Measuring Bacteria

Postby kevinliu18 » Tue Feb 18, 2014 6:47 pm

Thanks for your advise :)
Just making sure, would I need any sort of permit/license to use this type of bacteria (typically/State of California)?
Also other than E-Coli are there any other alternatives of bacteria cultures that would also be appropriate to use?

* I also say that some cultures were in vial and tubes-- is there a significant difference in them and would it matter if I used one over the other?

SciB
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Re: Measuring Bacteria

Postby SciB » Tue Feb 18, 2014 7:54 pm

Hi Kevin,

The E coli K12 strain has been genetically altered to be safe, i.e., not pathogenic, and it is the commonest variety used in the lab for genetic experiments. You don't need any licenses to buy and use it. There are safe handling procedures that you need to practice, but those are described in the link i sent you on bacterial use.

You are right--there IS a difference between the two types of E coli culture that Carolina Bio sells. One is growing on agar in a tube as colonies of bacteria and the other is 5 mL of a liquid culture in nutrient broth in a vial. Their descriptions are confusing because they both say 'agar culture' when one is actually in liquid, not on agar. I think the link i sent you is for the broth culture of E coli, #155068, which is the one that you need to spread on the plates. You can call customer service at Carolina Bio and confirm that #155068 IS the liquid culture.

The reason you need a LIQUID suspension of E coli bacteria is that you will take a bit of it (50-100 microliters) and spread it evenly on the plates to make what is called a 'lawn'--an even distribution of bacteria growing over the surface of the agar. After spreading, you will place the test strips with your inhibitor onto the surface of the agar and incubate the plates upside down in a warm place--about 90F or 32C for 1-2 days. If one of the substances you put onto the paper disks inhibited the E coli, you will see a clear zone around it. The stronger the inhibition the wider will be the zone.

You talked about counting the bacteria and that is another way of testing substances for antibacterial effect. It is more involved than the 'zone-of-inhibition' method i just described, but it is more quantitative and you will be able to say what percentage of the bacteria were killed by a particular substance. To do this experiment you would need 100 mL of sterile nutrient broth, some sterile tubes and sterile saline for dilutions. The youtube videos i sent you show how to make serial dilutions, spread the bacteria on plates and count the colonies.

Let us know how you want to do the experiment and we can help you with setting up the proper controls, the concentration of antibacterial soap to test and the number of plates per test. You always want to do a minimum of three plates per test [or three disks per plate if you are doing the zone method] so you can take the average of your readings and do statistical tests on them.

Good luck!

Sybee

kevinliu18
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Re: Measuring Bacteria

Postby kevinliu18 » Tue Mar 04, 2014 9:27 pm

oops, I actually have set everything up and just need to test/ the bacteria. I will be putting e-coli on agar in an incubator for a few days, what would be the optimal temperature for this?

Your prompt response will be appreciated,
Kevin

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Re: Measuring Bacteria

Postby JMP » Wed Mar 05, 2014 8:54 am

The incubator should be at 37 degrees Celsius (98.6 degrees Fahrenheit), i.e. human body temperature, for optimal growth. At this temperature, you will see significant growth overnight. E. coli will grow somewhat at a lower temperature, but it will take them much longer to do so. Also, don't let the temperature get too high or you could kill the bacteria.

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Re: Measuring Bacteria

Postby padwini » Mon Mar 10, 2014 12:33 am

What is unique about the Virus Microbe compared to the Fungi and Bacteria Microbes? Fungi, Bacteria and Virus are all types of microbes and are all therefore Unique what is so Unique about the Virus Microbe?
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kevinliu18
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Re: Measuring Bacteria

Postby kevinliu18 » Wed Mar 12, 2014 10:43 pm

Hey, I completed my experiment with e-coli but one of the petri dishes had contamination. There are 2 types of microbes in the dish. Any ideas on which is e-coli and what is the other one?

I could not add an attachment but here is why I observe.

1) One microbe is white, completely round, not fuzzy or irregular at all, and is elevated. Almost kinnda like a button
2) One microbe is grey with a large black center, fuzzy, round ( not irregular), and its edge are white. Basically a white fussy
circle with a large black center.


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